A platform with perfect horizontal straightness provides a basic guarantee for the precision measurement and manufacture of large scale integrated circuits in the field of super-precision measurement and manufacturing. It is widely used for many advanced production and measurement systems such as biology study, electron optics manufacture, precision machining, physical and chemical tests and etc. The control of its horizontal straightness has its effect on the measurements of machinery and the performance of instruments and directly effects on the suppression of platform with aerostatic floatation on vibration. The effect of environmental vibration on instrument and equipment increases as the super-precision measurement instrument and super-precision manufacturing instrument are increasingly updated. As a newly developed vibration isolation device, the platform with an electromagnetic and aerostatic floatation is developing with the development of precision instrument manufacture industry, the high speed development of ultra-large scale integrated circuits manufacture industry in particular, and as the measurement accuracy and stability requirements are becoming increasingly stringent as well.
Interferences to super-precision measurement instrument and manufacturing equipment are mainly generated at frequencies in the range of 0.8˜100 Hz. There are two kinds of vibration sources, one comes from the ground and the other comes from the platform itself. Passive isolation system is widely used to separate the platform from ground vibration. A passive isolation system usually does an excellent job at high frequency. But it does not work very well at low frequency and in reducing direct disturbance to the platform. So active isolation systems are now becoming more and more popular, because of their excellent vibration isolation performances. However, these active isolation systems need sensitive sensors and a large amount of energy from actuators. And the high cost of these systems places another obstacle to their further applications.
Taksehi Mizuno from Japan Saitama University used zero-power control strategy and proposed a magnetic suspension structure, to realize infinite stiffness and to reduce the direct disturbance. They proposed a solution to the problems of vibration isolation, but their proposed method still has its obvious drawback. The isolator's size and carrying capacity are limited because vibration isolation is achieved using mechanical springs. In addition, the position accuracy of the platform cannot go up to a micron or submicron level. Nowadays, there is a common problem with active or passive vibration isolation systems, such as complex structure, high manufacturing cost and stringent requirement for sensors and actuators.